The invention relates to a circuit for checking the operating state or status of a sensor. The sensor can either be operational or can transmit an erroneous signal which is caused in particular by a short circuit to ground, a short circuit to the supply voltage or by an interruption.
In the following, the expression "electron receiving electrode" is employed in connection with transistors, etc. This refers to the drain or collector in transistors with n-type conduction and to the source or emitter in transistors with p-type conduction.
Automatic status detection is particularly important for sensors which can only be observed and monitored at longer intervals of time or which supply their signals to fully-automated processing devices. In such cases it is standard to monitor operating parameters continuously and to generate binary status signals.
When checking the operation of a sensor it is desirable to be able to detect different operating states in the simplest manner possible. Accordingly, the problem arises of providing a testing or monitoring circuit for a sensor which makes it possible to distinguish between different operating states in a simple manner.